Try to use fabric loom in Termux Android but something could not be downloaded

[Silvigarabis]

Description

I was trying build something with fabric-loom 1.5.8 but it failed in there: https://github.com/FabricMC/fabric-loom/blame/713e1ff268df3b3ff1f5963f9bc3ac7b221e7666/src/main/java/net/fabricmc/loom/util/download/Download.java#L284

try {
	// Once the file has been fully read, create a hard link to the destination file.
	// And then remove the temporary file, this ensures that the output file only exists in fully populated state.
	Files.createLink(output, partFile); //this line thrown
	Files.delete(partFile);
} catch (IOException e) {
	throw error(e, "Failed to complete download");
}

and the log below:

Caused by: java.nio.file.AccessDeniedException: /data/data/com.termux/files/home/.gradle/caches/fabric-loom/1.20.4/minecraft-info.json -> /data/data/com.termux/files/home/.gradle/caches/fabric-loom/1.20.4/minecraft-info.json.part
        at java.base/sun.nio.fs.UnixException.translateToIOException(UnixException.java:90)
        at java.base/sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:106)
        at java.base/sun.nio.fs.UnixFileSystemProvider.createLink(UnixFileSystemProvider.java:492)
        at java.base/java.nio.file.Files.createLink(Files.java:1112)
        at net.fabricmc.loom.util.download.Download.downloadToPath(Download.java:284)
        ... 192 more

(full logs can be found there: https://paste.gg/p/anonymous/c3b2e8fcdaaf4e7eb62f7c84dd819244)

I'm certainly known this shouldn't happen in a normal linux environment, but I was working on Termux Android, and Android don't allow app to create hard link for a file. So it has failed.

Previously I was using fabric-loom 1.3.10 and it completed the build normally. After a simple search, I found out why the new version of fabric-loom could not run normally in my environment, which is the code at the beginning.

I'm not sure, could this be supported? Use fabric-loom to complete the construction of Minecraft Fabric mod on Android.

[modmuss50]

I think this is possibly something we can fix. It might be ok for loom to just move the file instead of link + delete. I think technically on windows a move operation isnt atomic, but its highly unlikey to cause a real world problem.

Ideally this would throw an UnsupportedOperationException or something so we could know to fall back to a move 🤔

[Silvigarabis]

In practice this is unlikely to be avoided by detecting UnsupportedOperationException. Technically, it's Android's Selinux policy that prevents the creation of hard links, so the error thrown will only be related to file permissions.
"When catching an error that you don't have permission to creating a link, use move instead" is probably not a good idea. But it is the most direct way, if you would like to make it compatible with Android. Therefore I did not treat this error as a bug.

[modmuss50]

I have removed the link from the latest 1.6.2 version here: https://github.com/orgs/FabricMC/discussions/3659 please let me know how you get on with this version.

[Silvigarabis]

It works! Thank you so much! I imagine this would be useful for someone just like me.

Starting a Gradle Daemon (subsequent builds will be faster)

> Configure project :
Fabric Loom: 1.6.2
:remapping 54 mods from modImplementation (java-api)
:remapping sources

> Task :tasks

------------------------------------------------------------
Tasks runnable from root project 'mafish-learning-cloned'
------------------------------------------------------------

Build tasks
-----------
assemble - Assembles the outputs of this project.
build - Assembles and tests this project.
buildDependents - Assembles and tests this project and all projects that depend on it.
buildNeeded - Assembles and tests this project and all projects it depends on.
classes - Assembles main classes.
clean - Deletes the build directory.
jar - Assembles a jar archive containing the classes of the 'main' feature.
sourcesJar - Assembles a jar archive containing the main sources.
testClasses - Assembles test classes.

Build Setup tasks
-----------------
init - Initializes a new Gradle build.
wrapper - Generates Gradle wrapper files.

Documentation tasks
-------------------
javadoc - Generates Javadoc API documentation for the 'main' feature.

Fabric tasks
------------
configureClientLaunch - Setup the required files to launch the Minecraft client
configureLaunch - Setup the required files to launch Minecraft
downloadAssets - Downloads required game assets for Minecraft.
generateDLIConfig - Generate the DevLaunchInjector config file
generateLog4jConfig - Generate the log4j config file
generateRemapClasspath - Generate the remap classpath file
genSources - Decompile minecraft using the default decompiler.
genSourcesWithCfr - Decompile minecraft using Cfr.
genSourcesWithFernFlower - Decompile minecraft using FernFlower.
genSourcesWithVineflower - Decompile minecraft using Vineflower.
migrateMappings - Migrates mappings to a new version.
remapJar - Remaps the built project jar to intermediary mappings.
remapSourcesJar - Remaps the default sources jar to intermediary mappings.
runClient - Starts the 'null' run configuration
runDatagen - Starts the 'Data Generation' run configuration
runServer - Starts the 'null' run configuration

Help tasks
----------
buildEnvironment - Displays all buildscript dependencies declared in root project 'mafish-learning-cloned'.
dependencies - Displays all dependencies declared in root project 'mafish-learning-cloned'.
dependencyInsight - Displays the insight into a specific dependency in root project 'mafish-learning-cloned'.
help - Displays a help message.
javaToolchains - Displays the detected java toolchains.
outgoingVariants - Displays the outgoing variants of root project 'mafish-learning-cloned'.
projects - Displays the sub-projects of root project 'mafish-learning-cloned'.
properties - Displays the properties of root project 'mafish-learning-cloned'.
resolvableConfigurations - Displays the configurations that can be resolved in root project 'mafish-learning-cloned'.
tasks - Displays the tasks runnable from root project 'mafish-learning-cloned'.

IDE tasks
---------
cleanEclipse - Cleans all Eclipse files.
cleanEclipseRuns - Removes Eclipse run configurations for this project.
cleanIdea - Cleans IDEA project files (IML, IPR)
eclipse - Generates all Eclipse files.
genEclipseRuns - Generates Eclipse run configurations for this project.
genIdeaWorkspace - Generates an IntelliJ IDEA workspace from this project.
idea - Generates IDEA project files (IML, IPR, IWS)
ideaSyncTask
openIdea - Opens the IDEA project
vscode - Generates VSCode launch configurations.

Publishing tasks
----------------
generateMetadataFileForMavenJavaPublication - Generates the Gradle metadata file for publication 'mavenJava'.
generatePomFileForMavenJavaPublication - Generates the Maven POM file for publication 'mavenJava'.
publish - Publishes all publications produced by this project.
publishMavenJavaPublicationToMavenLocal - Publishes Maven publication 'mavenJava' to the local Maven repository.
publishToMavenLocal - Publishes all Maven publications produced by this project to the local Maven cache.

Verification tasks
------------------
check - Runs all checks.
test - Runs the test suite.
validateAccessWidener - Validate all the rules in the access widener against the Minecraft jar

Rules
-----
Pattern: clean<TaskName>: Cleans the output files of a task.
Pattern: build<ConfigurationName>: Assembles the artifacts of a configuration.

To see all tasks and more detail, run gradle tasks --all

To see more detail about a task, run gradle help --task <task>

BUILD SUCCESSFUL in 9m 8s
1 actionable task: 1 executed